package demo2;

public class MyLinkedList {



    static class ListNode{
        private int val ;
        private ListNode next ;
        private ListNode prev ;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head ;
    public ListNode last ;



    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(this.head == null){
            this.head = node;
            this.last = node ;
        }else{
            node.next = this.head ;
            this.head.prev = node ;
            this.head = node ;
        }

    }
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(this.last == null){
            this.head = node ;
            this.last = node ;
        }else{
            last.next = node ;
              node.prev = this.last ;
            this.last = node ;
        }

    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        checkIndex(index);
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == size()) {
            addLast(data);
            return;
        }
            ListNode cur = searchIndex(index);
            ListNode node = new ListNode(data);
             node.prev = cur.prev ;
             node.next = cur ;
             cur.prev.next = node ;
             cur.prev = node ;

    }
    private ListNode searchIndex(int index){
        ListNode cur = this.head ;
        while (index>0){
            cur = cur.next ;
            index-- ;
        }
        return cur ;
    }
    private void checkIndex(int index){
        if(index<0 || index>size()){
            throw new IndexOutOfException("index: "+index+" 不合法") ;
        }
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = this.head ;
        while(cur!=null){
            if(cur.val == key){
                return true ;
            }
            cur = cur.next ;
        }
        return false ;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
       ListNode cur = this.head ;
       while(cur != null){
           if(cur.val == key){
               if(cur == head && cur == last){
                this.head = null ;
                this.last = null ;
               }else if (cur == this.head){
                   head = head.next ;
                   head.prev = null ;
               }else if(cur == last){
                   last = last.prev ;
                   last.next =null ;
               }else {
                   cur.prev.next = cur.next ;
                   cur.next.prev = cur.prev ;
               }
             return;
           }else {
                  cur = cur.next ;
           }
       }




    }


    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur = this.head ;
        while(cur != null) {
            if (cur.val == key) {
                if (cur == head && cur == last) {
                    this.head = null;
                    this.last = null;
                } else if (cur == this.head) {
                    head = head.next;
                    head.prev = null;
                } else if (cur == last) {
                    last = last.prev;
                    last.next = null;
                } else {
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }

            }
            cur = cur.next;
        }
    }


    //得到单链表的长度
    public int size(){
        int count = 0 ;
        ListNode cur = this.head ;
        while(cur!=null){
            count++ ;
            cur= cur.next ;
        }
        return count ;
    }
    public void display(){
        ListNode cur = this.head ;
        while(cur!=null){
            System.out.print(cur.val+"  ");
            cur = cur.next ;
        }
        System.out.println();
    }
    public void clear(){
       ListNode cur = this.head ;
       while(cur!=null){
             ListNode curNext = cur.next ;
           cur.prev = null ;
           cur.next = null ;
           cur = curNext ;
       }
       this.head = null ;
       this.last = null ;

    }


}
